Sheet manufacturing apparatus and sheet manufacturing method

ABSTRACT

A sheet manufacturing apparatus is provided with a defibrating unit configured to defibrate a defibration object in the atmosphere, a mixing unit configured to mix additive agents including resin into a defibrated material, a moisture-adjusting unit configured to adjust moisture in a mixture of the defibrated material and the additive agents, and a heating unit configured to heat the moisture-adjusted mixture.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2014-010156 filed on Jan. 23, 2014. The entire disclosure of JapanesePatent Application No. 2014-010156 is hereby incorporated herein byreference.

BACKGROUND

1. Technical Field

The present invention relates to a sheet manufacturing apparatus and asheet manufacturing method.

2. Related Art

Conventionally, fibrous materials are deposited and coupling forces actbetween the deposited fibers to obtain a sheet-like or film-like moldedbody. A representative example is the manufacture of paper by paperforming that uses water. Currently, paper forming is widely used as amethod for manufacturing paper. Generally, paper manufactured by paperforming has a structure in which cellulose fibers originating from, forexample, wood materials are entangled and are partially bonded bybonding forces such as hydrogen bonds.

However, paper forming is a wet type process requiring large quantitiesof water. In addition, after the paper has been formed, the need arisesfor dehydration and drying; therefore, the energy and time consumedbecome extremely large. Furthermore, the water used must beappropriately treated as wastewater. The apparatus used in paper formingoften require large-scale utilities and infrastructure for water, power,and wastewater facilities, and is difficult to reduce in size.

Thus, from the perspective of saving energy and protecting theenvironment, methods that use almost no water, referred to as dry typemethods, are anticipated as paper manufacturing methods that willreplace paper forming. For example, Japanese Laid-Open PatentApplication No. 2012-144819 discloses a paper recycling apparatus thatdefibrates and deinks the paper that becomes the raw material, adds asmall amount of moisture, and forms the paper in a dry type process.

The performance demanded from sheets, such as paper, is mechanicalstrength, for example, tensile strength and tear resistance. In thetechnology described in Japanese Laid-Open Patent Application No.2012-144819, the water moisture added during the formation of paper isbelieved to act to elicit hydrogen bonds originating in hydrogen groupsas the bonding force between the fibers forming the paper. However,after the paper has been formed, the hydrogen bonds will have reducedbonding force in the presence of water. Therefore, in paper in whichhydrogen bonding is used as the coupling force between the fibers,inadequate mechanical strength and shape deformation arise when thepaper is placed in a high-humidity environment or is dampened by water.Consequently, binding a plurality of fibers with resin was considered.However, mechanical strength was inadequate at times even when bonded byresin. The cause was the lower moisture content contained in the fiberswhen the sheet was formed. One cause of the lower moisture contentcontained in the fibers was the loss of moisture during defibration in adry type process when paper having relatively low moisture content wasthe raw material. Another cause was the lower moisture contentoriginally included in the paper that became raw materials. This occurswhen the manufacturing apparatus was installed in a low-humidityenvironment, and when the paper raw materials were placed in alow-humidity environment.

SUMMARY

One objective related to several embodiments of the present invention isto provide a sheet manufacturing apparatus and a sheet manufacturingmethod that are capable of manufacturing sheets having good mechanicalstrength and water resistance by using a dry type process.

The present invention solves at least a portion of the problemsdescribed above and can be implemented in the following embodiments orapplication examples.

One aspect of a sheet manufacturing apparatus related to the inventioncomprises a defibrating unit configured to defibrate in the atmosphere adefibration object, a mixing unit configured to mix in the atmosphereadditive agents containing resin into a defibrated material that hasbeen defibrated, a moisture-adjusting unit configured to adjust moisturein a mixture of the defibrated material and the additive agents, and aheating unit configured to heat the moisture-adjusted mixture that hasbeen moisture-adjusted.

According to this sheet manufacturing apparatus, because the fibers ofthe defibrated material are bonded by resin, even when the manufacturedsheet is placed, for example, in a high-humidity environment or isdampened by water, bonds in the defibrated material the manufacturedsheet are maintained by the resin. Therefore, the sheet has good waterresistance in which mechanical strength is maintained and shapedeformation is difficult. Additionally, a sheet having good mechanicalstrength can be manufactured by a dry type system because there is amoisture-adjusting unit to adjust the moisture of a mixture ofdefibrated material and additive agents, and fibers having theappropriate moisture content are used to produce the sheet.

The sheet manufacturing apparatus related to the aspect of the inventionmay have a deposition unit configured to deposit the mixture that hasbeen mixed by the mixing unit. The moisture-adjusting unit may beconfigured to adjust the moisture of the mixture deposited by thedeposition unit.

According to this sheet manufacturing apparatus, the moisture of themixture can be adjusted after the mixture has been deposited. Thus, themoisture content provided to the mixture by the moisture-adjusting unitis more easily supplied to the entire mixture (deposited material).Therefore, the strength of the manufactured sheet can be furtherincreased.

The moisture-adjusting unit in the sheet manufacturing apparatus relatedto the aspect of the invention may be configured to adjust the moisturesuch that a moisture content is from 5 parts by weight to 12 parts byweight with respect to 100 parts by weight of the mixture beforemoisture adjustment.

According to this sheet manufacturing apparatus, the amount of wateradded by the moisture-adjusting unit is more appropriate; and themechanical strength of the manufactured sheet can be increased when asmall amount of water is used. In addition, excess moisture content canbe suppressed even when in a high-humidity environment or when rawmaterials containing a high level of moisture are used.

The moisture-adjusting unit in the sheet manufacturing apparatus relatedto the aspect of the invention may be configured to adjust the moisturesuch that a moisture content of the mixture after moisture adjustment isgreater than a moisture content included in the defibration object.

According to this sheet manufacturing apparatus, there is more thanadequate compensation for the loss of moisture content in thedefibrating unit.

In the sheet manufacturing apparatus related to the aspect of theinvention, the moisture content provided to the mixture by themoisture-adjusting unit may be changed in accordance with at least oneof conditions of the moisture content of the defibration object,humidity of the environment, and temperature.

According to this sheet manufacturing apparatus, even if at least one ofthe conditions of the moisture content of the defibration object, thehumidity of the environment, and the temperature varies, fluctuationscan be suppressed in the mechanical strength and in the water resistanceof the manufactured sheet. Thus, a more stable sheet can bemanufactured.

An embodiment of the sheet manufacturing method related to one aspect ofthe invention includes defibrating in the atmosphere a defibrationobject, mixing in the atmosphere additive agents containing resin into adefibrated material that has been defibrated, adjusting moisture of amixture of the defibrated material and the additive agents, and heatingthe mixture that has been moisture-adjusted.

A sheet provided with bonding forces between the fibers of thedefibrated material by bonding with resin can be manufactured accordingto this sheet manufacturing method. A sheet manufactured by this sheetmanufacturing method has good water resistance in which mechanicalstrength is maintained and shape deformation is difficult, because bondsin the defibrated material are maintained by resin even when placed in ahigh-humidity environment or when dampened by water. In addition, asheet having good mechanical strength can be manufactured by a dry typemethod because moisture is adjusted in the mixture obtained by themixing process that mixes defibrated material and additive agents, andfibers having the appropriate moisture content are used to create asheet.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a schematic diagram illustrating a sheet manufacturingapparatus related to the embodiments;

FIGS. 2A-2D are schematic diagrams illustrating several examples ofcross-sections of composites related to the embodiments; and

FIG. 3 is a schematic diagram of important parts of the sheetmanufacturing apparatus related to the embodiments.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Several embodiments of the present invention will be described below.These embodiments describe examples of the present invention. Thepresent invention is not limited to the following embodiments andincludes various modified embodiments implemented within a scope thatdoes not change the intent of the present invention. All of theconfigurations described below do not limit the essential configurationsof the present invention.

1. Sheet Manufacturing Apparatus

A sheet manufacturing apparatus 100 related to the embodiment has adefibrating unit 20, a mixing unit 30, a moisture-adjusting unit 40, anda heating unit 50. FIG. 1 is a schematic diagram illustrating the sheetmanufacturing apparatus 100 related to the embodiment. The sheetmanufacturing apparatus 100 of the embodiment is described belowcentered on the defibrating unit 20, the mixing unit 30, themoisture-adjusting unit 40, and the heating unit 50.

1.1. Defibrating Unit

The defibrating unit 20 defibrates the defibration object. Thedefibrating unit 20 produces defibrated material refined into a fibrousform. The defibrating unit 20 also has a function that separates resinparticles or granular materials, such as inks, toners, orblur-preventing agents that are bonded to the defibration object fromthe fibers, for example, when the defibration object is used paper.

Here, the term “defibrating process” indicates the refining ofdefibration object of a plurality of bonded fibers into individualfibers. The term “defibrated material” indicates the material that haspassed through the defibrating unit 20. The term “defibrated material”also includes resin particles (resin for mutual bonding of a pluralityof fibers) and ink particles of inks, toners, and blur-preventing agentswhen the fibers are refined, in addition to the refined fibers. Theshapes of the refined defibrated material are string and ribbon shapes.The refined defibrated material may be in a form in which there is noentanglement with other refined fibers (independent form) or a form ofentangled clumps of refined defibrated material (formed into a so-called“dam (lump)”).

Furthermore, the terms “upstream” and “downstream” in this specificationare used with respect to the flow (including the conceptual flow) of thematerials of the manufactured sheet (e.g., raw materials, defibrationobject, defibrated material, and web) in the sheet manufacturingapparatus. The term “upstream” (“downstream”) is a relativespecification of the position in the configuration. For example, “A isupstream (downstream) of B” means that the position of A is upstream(downstream) with respect to the position of B with reference to theflow direction of the sheet material.

The defibrating unit 20 is provided further upstream than the mixingunit 30 to be described later. Other structures may be provided betweenthe defibrating unit 20 and the mixing unit 30. In addition, otherstructures may be provided further upstream than the defibrating unit20.

An option of the defibrating unit 20 is to be limited to having afunction that defibrates the defibration object. The defibrating unit 20defibrates in a dry type system in the atmosphere (in air). In theexample shown, the defibration object that is introduced from anintroduction port 21 is defibrated by the defibrating unit 20 to becomedefibrated material (fibers). The defibrated material discharged from adischarge port 22 is supplied through a pipe 82 and a classifier unit 63to the mixing unit 30 (through pipe 86 in the example shown).

In this specification, a dry type system refers to use in the atmosphere(in air) and not in liquid. The dry type system category includes thedry state and the state in which a liquid (e.g., water) is present as animpurity or in which a liquid (e.g., water), water vapor, or mist hasbeen intentionally added. It should be noted that in a dry type systemand a wet type system, such as paper forming, the amounts of water usedare completely different depending on the entire apparatus and thequantity of paper to be manufactured. That is, the amount of water whenwater is in a dry type system is an order of magnitude smaller than thatin a wet type system.

The configuration of the defibrating unit 20 is not particularlyrestricted, and may include, for example, a rotary unit (rotor) and astationary unit as a cover thereof, and a gap can be formed between therotary unit and the stationary unit. In a defibrating unit 20 havingthis configuration, defibration is conducted by introducing thedefibration object into the gap while the rotary unit is rotating. Inthis case, the rotational speed and the shape of the rotary unit and theshape of the stationary unit can be appropriately designed to satisfydemands such as the quality of the manufactured sheet and the overallconfiguration of the apparatus. Additionally, in this case, therotational speed of the rotary unit (rotations per minute (rpm)) can beappropriately set when taking into consideration conditions that includethe throughput of the defibration process, the residence time of thedefibration object, the extent of defibration, the size of the gap, andthe shapes and sizes of the rotary unit, stationary unit, and otherparts.

More preferably, the defibrating unit 20 has a function that generatesairflow in order to draw in the defibration object and/or to dischargethe defibrated material. In this case, the defibrating unit 20 generatesairflow and uses the generated airflow to draw in the defibration objectfrom the introduction port 21, defibrates, and transfers the defibratedmaterial to the discharge port 22. In the example shown in FIG. 1, thedefibrated material discharged from the discharge port 22 is transferredin a pipe 82. If the defibrating unit 20 used does not have a mechanismfor generating airflow, a mechanism that generates airflow forintroducing defibration object to the introduction port 21 or generatesairflow for discharging the defibrated material through the dischargeport 22 may be installed externally.

1.1.1. Defibration Object

In this specification, the defibration object indicates productscontaining the raw materials of the sheet manufacturing apparatus 100.For example, these materials have entangled or bonded fibers and includepulp sheets, paper, used paper, tissue paper, paper towels, cleaningcloths, filters, liquid-absorbing materials, sound absorbing materials,cushioning materials, mats, and cardboard. In addition, the defibrationobject may include fibers (organic fibers, inorganic fibers, hybridorganic-inorganic fibers) consisting of rayon, lyocell, cupro, vinylon,acrylic, nylon, aramid, polyester, polyethylene, polypropylene,polyurethane, polyimide, carbon, glass, and metal. If a classifier unit63, which is described later, is provided in the sheet manufacturingapparatus 100 of this embodiment, used paper, in particular, can beeffectively used as the defibration object.

1.1.2. Defibrated Material

In the sheet manufacturing apparatus 100 of this embodiment, thedefibrated material used as a part of the materials of the manufacturedsheet is not particularly limited, and may be any material in a widerange of defibrated materials that can be formed into a sheet. Thedefibrated materials include fibers obtained by defibrating thematerials to be defibrated described above. The fibers may be naturalfibers (animal fibers, plant fibers) and synthetic fibers (organicfibers, inorganic fibers, hybrid organic-inorganic fibers). Morespecifically, the fibers included in the defibrated material may becomposed of cellulose, silk, wool, cotton, hemp, kenaf, flax, ramie,jute, Manila hemp, sisal hemp, conifer, and broadleaf trees. Thesefibers may be used individually, appropriately mixed, or used asrecycled fibers that have been refined. Defibrated materials become thematerials of the manufactured sheet and may include at least one ofthese fibers. Additionally, the defibrated materials (fibers) may bedried, or may contain or absorb liquids such as water or organicsolvents.

Furthermore, the defibrated materials (fibers) may be subjected tovarious surface processes.

When the fibers are individual fibers, the mean diameter of the fibersincluded in the defibrated materials used in this embodiment is from 1μm to 1000 μm; preferably, from 2 μm to 500 μm; and more preferably,from 3 μm to 200 μm (when the cross section is not circular, the largerof the lengths in the lengthwise and perpendicular directions, or thediameter of a circle having an area assumed to be equal to that of thecross section (equivalent circle diameter)).

The lengths of the fibers included in the defibrated material used inthis embodiment are not particularly limited. For example, the length ofan individual fiber in the lengthwise direction of the fiber (hereafter,referred to as the “fiber length,” which is the length in the lengthwisedirection of the refined defibrated material (fibers)) is, in order tothe most preferred, from 1 μm to 10 mm, from 1 μm to 8 mm, from 1 μm to5 mm, from 2 μm to 3 mm, or from 3 μm to 2 mm. Because bonding to theadditive agents (composites) is difficult for short fiber lengths, thesheet strength is sometimes unsatisfactory. However, if the lengths arewithin the above ranges, sheets with satisfactory strength can beobtained. The length in the lengthwise direction of a fiber is thedistance between the two ends arranged in a nearly linear state (fiberlength) when an individual fiber is stretched at both ends as neededwithout breaking the fiber. The mean length of a fiber as thelength-length-weighted mean fiber length is from 20 μm to 3600 μm;preferably, from 200 μm to 2700 μm; and more preferably, from 300 μm to2300 μm. Furthermore, the fiber length may fluctuate (have adistribution).

In this specification, fiber indicates an individual fiber or anaggregate of a plurality of fibers (e.g., a state resembling cotton).Defibrated material indicates a material containing a plurality offibers, and includes fiber bundles and materials that become the rawmaterials of the sheet (materials in powder or cotton-like form).

1.2. Mixing Unit

The mixing unit 30 provided in the sheet manufacturing apparatus 100 ofthis embodiment has a function that mixes (mixes together) defibratedmaterial and additive agents containing resin in the atmosphere. Atleast defibrated material and additive agents are mixed together by themixing unit 30. Ingredients other than defibrated material and additiveagents may be mixed by the mixing unit 30. In this specification, thephrase “defibrated material and additive agents are mixed” means thatthe additive agents are positioned between the fibers contained in thedefibrated material within a constant volume space (system).

The configuration of the mixing unit 30 and the configuration andmechanisms thereof are not particularly limited if the mixing unit isable to mix defibrated material (fibers) and additive agents. Theprocess state of mixing in the mixing unit 30 may be a batch process, asequential process, or a continuous process. Additionally, the mixingunit 30 may be operated manually or operated automatically. Furthermore,the mixing unit 30 mixes at least defibrated material and additiveagents, but is able to mix other ingredients.

The mixing unit 30 is provided downstream of the defibrating unit 20described above. The mixing unit 30 is provided further upstream thanthe heating unit 50, which is described later. Structures in addition tothe moisture-adjusting unit 40, which is described later, may beincluded between the mixing unit 30 and the heating unit 50. The otherstructures may be a refining unit 70 that refines the mixture ofdefibrated material and additive agents, a deposition unit 75 that formsthe mixture into a web, or a pressing unit 60 that applies pressure tothe mixture deposited into a web shape (each unit will be describedlater), but is not limited to these units. The mixture mixed by themixing unit 30 may be further mixed by another structure, such as therefining unit 70. Thus, the refining unit 70 may also be regarded as amixing unit.

Examples of the mixing process in the mixing unit 30 are mechanicalmixing and hydrodynamic mixing. For example, mechanical mixing may be amethod in which fibers (defibrated material) and additive agents areintroduced into a Henschel mixer and stirred, or a method that seals thefibers (defibrated material) and additive agents in a pouch and agitatesthe pouch. In addition, the hydrodynamic mixing process may be a methodthat introduces fibers (defibrated material) and additive agents intoairflow of the atmosphere to mutually diffuse the materials in theairflow. In the method that introduces fibers (defibrated material) andadditive agents into airflow of the atmosphere, additive agents may befed into pipes in which fibers of defibrated material are flowing (beingtransferred) in the airflow, or fibers (defibrated material) may be fedinto pipes in which particles of the additive agents are flowing (beingtransferred) in the airflow. In these methods, more preferably,turbulent airflow in the pipes results in more efficient mixing.

The mixing unit 30 may be configured to include a feeder that introducesadditive agents into the circulation path of the defibrated material. Asillustrated in FIG. 1, when a pipe 86 is adopted to transfer defibratedmaterial as the mixing unit 30, a method can be adopted that introducesadditive agents by an additive agent supply unit 88 after the defibratedmaterial has been made to flow in airflow of, for example, theatmosphere. When the pipe 86 is used as the mixing unit 30, the airflowgeneration means may be a blower, which is not shown. The only limit onthe airflow generation means is the ability to carry out the abovefunctions.

When the pipe 86 is used as the mixing unit 30, additive agents(including composites) may be introduced by opening and closing valves,or manually by a worker. However, a screw feeder as shown in FIG. 1 or adisk feeder, which is not shown, may be used as the additive agentsupply unit 88. Use of these feeders is preferred because fluctuationsin the included amounts (added amounts) of additive agents in the flowdirection of the airflow can be reduced. The same applies when theadditive agents are transferred by airflow, and the defibrated materialis introduced into that airflow. In the illustrated examples, additiveagents are supplied from the additive agent supply unit 88 to the pipe86 through a supply port 87 provided in the pipe 86. Thus, in theillustrated example, the mixing unit 30 is configured from a portion ofthe pipe 86, the additive agent supply unit 88, and the supply port 87.

In the sheet manufacturing apparatus 100 of this embodiment, the mixingunit 30 is an embodiment of a dry type system. Here, “dry type system”for mixing is mixing that is conducted in the atmosphere (in air) andnot in liquid.

When a liquid is intentionally added to a degree that does not interferewith the mixing action in the mixing unit 30, preferably, the liquid isadded so that the energy and time needed in order to remove the liquidin subsequent processes by heating do not become too large.

As long as defibrated material and additive agents can be mixed, theprocessing capacity of the mixing unit 30 is not particularly limitedand can be appropriately designed and adjusted in response to themanufacturing capacity (throughput) of the sheet manufacturing apparatus100. If batch processing is used, the processing capacity of the mixingunit 30 can be adjusted by changing the size of the processing vesseland the charged amount. Additionally, when the pipe 86 and the additiveagent supply unit 88 described above are adopted as the mixing unit 30,the flow rate of air for transferring defibrated material and additiveagents in the pipe 86, the introduced amount of materials, and theamount transferred can be changed. Defibrated material and additiveagents can be satisfactorily mixed when the pipe 86 and the additiveagent supply unit 88 as shown are adopted as the mixing unit 30.

The additive agents supplied from the additive agent supply unit 88include resin for bonding a plurality of fibers. When additive agentsare supplied to the pipe 86, there is no intentional mutual bondingbetween the plurality of fibers included in the defibrated materialexcept when the defibration was inadequate. The resin included in theadditive agents melts or softens when passed through the heating unit50, which is described later, and then hardens to bond the plurality offibers. When passed through the heating unit 50, the plurality of fibersis bonded by hydrogen bonds by removing moisture that was supplied bythe moisture-adjusting unit 40.

1.2.1. Additive Agents

The additive agents supplied from the additive agent supply unit 88include resins. The types of resins may be natural resins or syntheticresins, or may be thermoplastic resins or thermosetting resins. In thesheet manufacturing apparatus 100 of this embodiment, preferably, theresin is solid at room temperature, and is a thermoplastic resin, inlight of the bonding of the fibers by heat in the heating unit 50.

The natural resins may be rosin, dammar, mastic, copal, amber, shellac,dragon's blood, sandarac, or colophony. These resins may be usedseparately or appropriately mixed. Resins may be subjected toappropriate chemical modification.

Thermosetting resins among the synthetic resins may be phenolic resins,epoxy resins, melamine resins, urea resins, unsaturated polyesterresins, alkyd resins, polyurethane, or thermosetting polyimide resins.

The thermoplastic resins among the synthetic resins may beacrylonitrile-styrene resins, acrylonitrile-butadiene-styrene resins,polypropylene, polyethylene, polyvinyl chloride, polystyrene, acrylicresin, polyester resin, polyethylene terephthalate, polyphenylene ether,polybutylene terephthalate, nylon, polyamide, polycarbonate, polyacetal,polyphenylene sulfide, or polyether ether ketone.

These resins may be used individually or appropriately mixed. Inaddition, the resins may be copolymerized or modified. These resinsystems may be styrene-based resins, acrylic-based resins,styrene-acrylic-based copolymer resins, olefin-based resins,vinyl-chloride-based resins, polyester-based resins, polyamide-basedresins, polyurethane-based resins, polyvinyl-alcohol-based resins,vinyl-ether-based resins, N-vinyl-based resins, orstyrene-butadiene-based resins.

The forms of the additive agents may be fibers or powders. If theadditive agents are fibers, the preferred fiber length of an additiveagent is less than the fiber length of the defibrated material.Specifically, the fiber length of an additive agent is 3 mm or less, ormore preferably, 2 mm or less. If the fiber length of an additive agentis longer than 3 mm, sometimes, more uniform mixing with the defibratedmaterial becomes difficult. If the additive agent is a powder, the grainsize (diameter) of the additive agent is from 1 μm to 50 μm, orpreferably, from 2 μm to 20 μm. If the grain size of the additive agentis less than 1 μm, sometimes, the bonding force for bonding together thefibers in the defibrated material is reduced. If the grain size of theadditive agent is greater than 20 μm, sometimes, good uniform mixingwith the defibrated material is difficult; the bonding force to thedefibrated material is reduced; the additive agents separate from thedefibrated material; and the manufactured sheet is uneven.

The amount of additive agents supplied from the additive agent supplyunit 88 is appropriately set to correspond to the type of manufacturedsheet. For example, the proportion of additive agents with respect tothe defibrated material is from 5% by weight to 70% by weight. From theperspective of obtaining a well-mixed mixture in the mixing unit 30 andthe perspective of preventing the additive agents from falling off dueto gravity when the mixture is formed into a web shape, the preferredamount is from 5% by weight to 50% by weight. In the example shown, thesupplied additive agents are mixed with the defibrated material in thepipe 86 that is configured as the mixing unit 30.

The additive agents may include other ingredients in addition to resin.The other ingredients may be coagulation inhibitors, colorings, organicsolvents, surfactants, anti-mildew agents, antiseptic agents,anti-oxidation agents, ultraviolet light-absorbing agents, andoxygen-absorbing agents. The coagulation inhibitors and the coloringsare described in detail below.

1.2.1.1. Coagulation Inhibitors

In addition to resins for bonding the defibrated material, additiveagents may also include coagulation inhibitors in order to suppresscoagulation between the fibers in the defibrated material andcoagulation between resins in the additive agents. When a coagulationinhibitor is included in the additive agents, preferably, the resin andthe coagulation inhibitor are integrated into one body. Specifically,when the coagulation inhibitor is included in the additive agent,preferably, the additive agent is a composite having the resin and thecoagulation inhibitor in one body.

In this specification, composites are particles composed of resin as oneingredient and another ingredient that are formed into one body. Theother ingredient may be a coagulation inhibitor or a coloring, andincludes ingredients that have forms, sizes, substances, and functionsthat differ from those of the resin, which is the main ingredient.

In a comparison of combining the coagulation inhibitor with the additiveagent and not combining with the coagulation inhibitor, the resin andthe coagulation inhibitor are more difficult to mutually coagulate whenintegrated into one body in a composite. Various types of coagulationinhibitors may be used, but in the sheet manufacturing apparatus 100, atype that is arranged on the surface of the composite (such as acoating) is preferred because water is not used or almost no water isused in the mixing unit 30.

This coagulation inhibitor is composed of fine particles composed ofinorganic matter, but is able to obtain a superior coagulationinhibition effect when arranged on the surface of the composite.Coagulation refers to the state in which identical or different bodiesare physically connected by electrostatic forces or van der Waalsforces. Additionally, the uncoagulated state for an aggregate of aplurality of bodies (e.g., powders) does not necessarily indicate thatall of the bodies forming the aggregate are in a dispersed arrangement.That is, the uncoagulated state also includes the state in which aportion of the bodies forming the aggregate has coagulated. The amountof these coagulated bodies is 10% by weight or less, preferablyapproximately 5% by weight or less, of the entire aggregate. This stateincludes the “uncoagulated state” in an aggregate of a plurality ofbodies. Furthermore, when a powder is packed, the powder particles arein contact with each other. The uncoagulated state includes the state inwhich the particles are dispersed by external forces that do not destroythe particles, such as gentle stirring, scattering by airflow, or freefall.

Specific examples of coagulation inhibitors are silica, titanium oxide,aluminum oxide, zinc oxide, selenium oxide, magnesium oxide, zirconiumoxide, strontium titanate, barium titanate, and calcium carbonate. Aportion of the materials used as coagulation inhibitors (e.g., titaniumoxide) is the same as those used as colorings. The difference is thatthe grain size of a coagulation inhibitor is smaller than the grain sizeof a coloring. Therefore, a coagulation inhibitor does not greatlyaffect the color tone of the manufactured sheet and can bedifferentiated from the coloring. However, when the color tone of thesheet is adjusted, some effects such as light scattering may occur evenif the grain size of the coagulation inhibitor is smaller. Preferably,these effects should be taken into account.

The mean grain size of the particles in the coagulation inhibitor (meandiameter of several particles) is not particularly specified, but ispreferably, 0.001 to 1 μm, or more preferably, 0.008 to 0.6 μm. Theparticles of the coagulation inhibitor are categorized as so-callednanoparticles and generally become the primary particles because theirgrain size is small. However, the particles of the coagulation inhibitormay be a plurality of primary particles bonded together to becomehigh-order particles. If the grain size of the primary particles in thecoagulation inhibitor is within the above range, good coating of thesurface of the resin is possible, and an adequate coagulation inhibitioneffect of the composite can be provided. Coagulation of composite powderin which coagulant inhibitors are arranged on the surfaces of resinparticles is suppressed because coagulation inhibitor is present betweenthe composites. The coagulation inhibition effect between resinparticles is considered to be less when the resin and the coagulationinhibitor are not integrated but are separate bodies compared to whenthey are integrated because coagulation inhibitor is not always presentbetween the resin particles.

The included amount of coagulation inhibitor in the composite of resinand coagulation inhibitor integrated into one body is preferably from0.1 parts by weight to 5 parts by weight with respect to 100 parts byweight of resin. For this included amount, the effects described abovecan be obtained. In addition, from the perspective of improving theabove effect and/or suppressing the falling off of the coagulationinhibitor from the manufactured sheet, the included amount is preferably0.2 parts by weight to 4 parts by weight, or more preferably, 0.5 partsby weight to 3 parts by weight with respect to 100 parts by weight ofresin.

When coagulation inhibitor is arranged on the surface of the resin, ifthe percentage of the composite surface that is coated with coagulationinhibitor (area ratio, sometimes referred to as coverage in thisspecification) is from 20% to 100%, a satisfactory coagulationinhibition effect can be obtained. Coverage can be adjusted by chargingto an apparatus like a fiber material (FM) mixer. Furthermore, if thespecific surface areas of the coagulation inhibitor and the resin areknown, adjustments are possible based on the mass (weight) of eachcomponent during charging. In addition, coverage can be measured byvarious electron microscopes. In a composite in which the coagulationinhibitor is arranged so that falling off of the resin is difficult, thecoagulation inhibitor and the resin can be integrated into one body.

If the coagulation inhibitor is combined with the composite, coagulationof the composite can become extremely difficult. Therefore, additiveagents (composites) and defibrated material can be more readily mixed inthe mixing unit 30. That is, when the coagulation inhibitor as acomposite of resin is combined in the additive agents, a uniform mixtureof defibrated material and additive agents can be formed more rapidly ascompared with the inability to mix in the coagulation inhibitor becauseof the rapid diffusion of the composite into the space.

The reason why the composites and the defibrated material can be mixedwell by airflow or by the stirring of the mixer by using a coagulationinhibitor is the tendency of the composites to readily develop staticelectricity when coagulation inhibitor is arranged on the surfaces ofthe composites, and the static electricity suppresses coagulation of thecomposites. Studies by the inventors showed that there is a highprobability that composites adhering to the fibers due to staticelectricity will not easily separate from the fibers even whenmechanical collisions occur. Because of this tendency, when thecoagulation inhibitor is combined with the additive agents as thecomposites, the composites are believed to not easily separate once theyadhere to the fibers and to rapidly mix without the use of special meansin addition to mixing the fibers with the composites. The actions of themixing unit 30 mix the defibrated material (fibers) and the composites.After the mixture is produced, adhesion of the composites to the fibersis stable, and separation of the composites is not seen.

1.2.1.2. Coloring

In addition to the resin that bonds the fibers of the defibratedmaterial, the additive agents may also include coloring. If coloring isincluded in the additive agents, preferably, the resin and the coloringare integrated into one body. That is, the additive agents arepreferably composites having resin and coloring in one body. Inaddition, even if the composite includes a coagulation inhibitor asdescribed above, the composite may have resin, coloring, and coagulationinhibitor formed in one body. That is, the additive agents may includecomposites that have resin, coagulation inhibitor, and coloring in onebody.

A composite having resin and coloring in one body refers to the state inwhich separation of the coloring (difficulty falling off) is difficultin the sheet manufacturing apparatus 100 and/or in the manufacturedsheet. A composite having resin and coloring in one body indicates thestate in which the coloring is mutually bonded by resin, the state inwhich the coloring is structurally (mechanically) fixed to the resin,the state in which the resin and the coloring are coagulated by staticelectricity or van der Waals forces, and the state in which the resinand the coloring are chemically bonded. The state in which the compositeis resin and coloring in one body may include the state of the coloringencapsulated by the resin or the state in which the coloring adheres tothe resin, and the state in which these two states coexist.

FIG. 2 schematically illustrates several states of the cross-sectionalplane of a composite having resin and coloring in one body. Examples ofthe specific state of a composite having resin and coloring in one bodyare a composite 3 that is configured to include a single coloring or aplurality of colorings 2 dispersed in a resin 1 as shown in FIGS. 2A toC, and a composite 3 in which a single coloring or a plurality ofcolorings 2 adheres to the surface of resin 1 as shown in FIG. 2D. Inthe sheet manufacturing apparatus 100 of this embodiment, an aggregate(powder) of these composites 3 may be used as the composite.

FIG. 2A illustrates an example of a composite 3 that has a constitutionin which a plurality of colorings 2 (represented as powder) is dispersedin resin 1 to form a composite 3. This type of composite 3 becomes aso-called island structure in which resin 1 is dispersed as the matrixand the coloring 2 as the domain. In this example, because the coloring2 is enclosed by the resin 1, it would be difficult for the coloring 2to pass through the resin part (matrix) and separate from the resin 1.Therefore, in the resulting state, it is difficult for coloring 2 tofall off of the resin part when subjected to various processes or whenformed into a sheet in the sheet manufacturing apparatus 100. Thedispersed state of coloring 2 in the composite 3 may have coloring 2 inmutual contact or may have resin 1 between the coloring 2. In FIG. 2A,the coloring 2 is dispersed throughout, but may be biased to one side.For example, the coloring 2 may be only on the right side or the leftside in the drawing. When the dispersion is biased to one side, thecoloring 2 may be arranged in the center portion of the resin 1 as inFIG. 2 B, or the coloring 2 may be arranged in a section close to thesurface of the resin 1 as in FIG. 2C. The resin 1 may have motherparticles 4 near the center and a shell 5 surrounding the particles. Themother particles 4 and the shell 5 may be mutually similar types ordifferent types of resins.

The example illustrated in FIG. 2D is a composite 3 in which thecoloring 2 is embedded near the surface of a particle composed of resin1. In this example, the coloring 2 is exposed at the surface of thecomposite 3, but has difficulty falling off of the composite 3 becausethe coloring adheres (chemical or physical bonding) to the resin 1 or ismechanically fixed by the resin 1. This type of composite 3 can besuitably used in the sheet manufacturing apparatus 100 of the embodimentas the composite 3 having resin 1 and coloring 2 in one body.

In this example, the coloring 2 may be arranged inside of and not onlyon the surface of the resin 1.

Several states of composites having resin and coloring in one body weredescribed. However, the state is not limited to states in which it isdifficult for the coloring to fall off of the resin when subjected tovarious processes or when the sheet is formed in the sheet manufacturingapparatus 100, and may be any state in which it is difficult for thecoloring to fall off of the resin is acceptable, such as the state inwhich the coloring adheres to the surfaces of the resin particles byelectrostatic forces or by van der Waals forces. In addition, even inthe state that is a combination of a plurality of the states describedabove, any state in which it is difficult for the coloring to fall offof the composite may be adopted.

The preferred arrangement in the composite of the coagulation inhibitordescribed in paragraph “1.2.1.1. Coagulation inhibitor” is conceptuallysimilar to the arrangement illustrated in FIG. 2D. However, it should benoted that the coagulation inhibitor has a smaller grain size than thecoloring 2. When a coloring is integrated into one body in any of thearrangements in FIGS. 2A to 2D, the coagulation inhibitor can be formedon the surface of the composite having resin and coloring in one body.

Coloring has a function of designating the color of the sheetmanufactured by the sheet manufacturing apparatus 100 of thisembodiment. The colorings may be dyes or pigments. When integrated intoone body with resin in a composite, preferably, pigments are used fromthe perspective of obtaining improved hiding power and colordevelopment.

The colors and types of pigments are not particularly limited. Forexample, pigments in the variety of colors used in common inks (e.g.,white, blue, red, yellow, cyan, magenta, black, and special colors(particularly, pearl and metallic luster)) can be used. The pigments maybe inorganic or organic pigments. The pigments may be the well-knownpigments described in Japanese Laid-Open Patent Application Nos.2012-87309 and 2004-250559. In addition, the white pigments may be zincoxide, titanium oxide, antimony white, zinc sulfide, clay, silica, whitecarbon, talc, and alumina white. These pigments may be used individuallyor in appropriate mixtures. If a white pigment of the pigments describedabove is used, a pigment composed of powder that includes particles(pigment particles) with titanium oxide as the main ingredient may beused, and is preferred because the refractive index of titanium oxide ishigh so the manufactured sheet has a high whiteness level with a smallblended amount of pigment.

In the mixing unit 30, defibrated material and additive agents describedabove are mixed together, but the mixing ratios thereof can be moreappropriately adjusted based on the strength, properties, and uses ofthe manufactured sheet. For example, if the manufactured sheet is foroffice use, such as copy paper, the percentage of additive agents withrespect to defibrated material is from 5% by weight to 70% by weight.From the perspective of obtaining a good mixture in the mixing unit 30and the perspective of inhibiting the falling off of additive agents dueto gravity when the mixture is formed into a web shape, the preferredpercentage is from 5% by weight to 50% by weight.

1.3. Moisture-Adjusting Unit

The moisture-adjusting unit 40 provided in the sheet manufacturingapparatus 100 of this embodiment has a function for adjusting themoisture of the mixture of defibrated material and additive agents fromthe mixing unit 30 described above. Here, moisture adjustment refers tothe addition of water and/or water vapor to the mixture to adjust theweight ratio of the mixture and water. The addition of water duringmoisture adjustment, for example, when the moisture-adjusting unit 40uses spraying, includes spraying an aqueous solution that contains wateras a solvent and spraying a dispersion liquid that contains water as thedispersion medium, in addition to adding water by spraying water.Furthermore, the addition of water during moisture adjustment includesusing water vapor (steam) to add water.

The moisture-adjusting unit 40 provides water to the mixture. When themoisture-adjusted mixture is heated in the heating unit 50, which isdescribed later, hydrogen bonds between the fibers of the sheet S thatis obtained are efficiently elicited by the evaporation of at least aportion of the water provided by the moisture-adjusting unit 40.

If the moisture-adjusting unit 40 can provide water to the mixture, theconfiguration, structure, and mechanisms thereof are not particularlylimited. The processing state of the moisture-adjusting unit 40 may be abatch process, a serial process, or a continuous process. In addition,the moisture-adjusting unit 40 may be operated manually orautomatically. Examples of specific configurations of themoisture-adjusting unit 40 include a configuration that sprays waterfrom a nozzle onto the mixture, a configuration that blows steam (watervapor), and a configuration that provides mist obtained from, forexample, ultrasonic vibrations.

The moisture-adjusting unit 40 is installed downstream of the mixingunit 30 as described above and upstream of the heating unit 50. Otherstructures may be installed between the mixing unit 30 and the heatingunit 50. The other structures may be, but are not limited to, a refiningunit 70 that refines the mixture of defibrated material and additiveagents, a deposition unit 75 that forms the mixture into a web shape, ora pressing unit 60 that applies pressure to the mixture deposited in theweb shape (each unit will be described later). However, when the sheetmanufacturing apparatus 100 is provided with a refining unit 70,preferably, the moisture-adjusting unit 40 is provided furtherdownstream than the refining unit 70 because of the potential of waterobstructing the refining operation of the refining unit 70. As in theillustrated examples, when the sheet manufacturing apparatus 100 isprovided with a deposition unit 75, the moisture-adjusting unit 40 maybe arranged downstream of the deposition unit 75 so that moisture isprovided to the web W of the deposited mixture. In this case, themoisture provided to the mixture by the moisture-adjusting unit 40 iseasily supplied to the entire mixture (deposited material). Therefore,the strength of the manufactured sheet can be further improved.

In the illustrated examples, the moisture-adjusting unit 40 is arrangeddownstream of the deposition unit 75 and upstream of the pressing unit60, but may be arranged downstream of the pressing unit 60. Furthermore,although not shown, the moisture-adjusting unit 40 may be arranged at aposition that enables providing moisture to the mixture that drops fromthe refining unit 70.

Furthermore, the moisture-adjusting unit 40 may be integrated with therefining unit 70 or the deposition unit 75. The moisture-adjusting unit40 may be configured to include, for example, pipes connected toexternal utility pipes, pumps, and various input and output terminals.

The moisture-adjusting unit 40 adjusts moisture so that the moisturecontent with respect to 100 parts by weight of the mixture beforemoisture adjustment is from 0.5 parts by weight to 20 parts by weight.If the moisture content provided by the moisture-adjusting unit 40 iswithin this range, hydrogen bonding can be elicited between the fibersin the manufactured sheet; the mechanical strength of the sheet can beimproved; and the amounts of water and energy used by the equipment canbe reduced. In order of increasing preference, the preferred moistureadjustments by the moisture-adjusting unit 40 are from 1 part by weightto 15 parts by weight of moisture content with respect to 100 parts byweight of the mixture, from 3 parts by weight to 14 parts by weight,from 5 parts by weight to 12 parts by weight, and from 7 parts by weightto 8 parts by weight. If the moisture is adjusted to this level, themechanical strength of the manufactured sheet S is good; and water andenergy can be efficiently used.

According to studies by the inventors, when the defibration object ispulp sheet, and the additive agent is a powder of polyester resin, thetensile strength and rupture stress of the formed sheet S is three foldor more when the moisture content provided to the mixture by themoisture-adjusting unit configured to spray water is from 5 parts byweight to 12 parts by weight with respect to 100 parts by weight of themixture than when a moisture content of 0 parts by weight (no additionof water by the moisture-adjusting unit) was provided.

The moisture content provided by the moisture-adjusting unit 40 can beadjusted by using valves to supply, for example, water. The moisturecontent can be adjusted to a predetermined value that takes into accountthe amount of material (defibration object) for the sheet manufacturingapparatus or the mass balance such as the throughput of the defibratingunit 20. In addition, the moisture content can be adjusted in responseto, for example, the mass balance of the apparatus, the moisture contentincluded in the defibration object, and the humidity of the installationenvironment of the apparatus.

The moisture-adjusting unit 40 may be configured to adjust the providedmoisture content based on information related to the moisture content,the humidity, and the temperature measured, for example, by a moisturecontent measuring unit, a humidity measuring unit, and a temperaturemeasuring unit, which are not shown. For example, the moisture contentof the mixture before and after moisture adjustment may be measured byapparatus based on well-known optical or electromagnetic principles thatare arranged at appropriate positions inside or outside of the sheetmanufacturing apparatus 100. In addition, the humidity and thetemperature can be measured by the commonly known hygrometer andthermometer that are arranged at appropriate positions inside or outsideof the sheet manufacturing apparatus 100. The sheet manufacturingapparatus 100 may have a control unit, which is not shown, to controlthe degree of opening of the valves based on these measurements.

The moisture-adjusting unit 40 may adjust the moisture so that themoisture content after adjusting the moisture of the mixture is muchgreater than the moisture content included in the defibration object.When moisture is included in the defibration object that becomes a partof the raw materials, a portion or all of the included moisture issometimes evaporated and lost when the defibration object passes throughthe defibrating unit 20 followed by the defibrated material passingthrough the mixing unit 30. In this case, the amount of moistureexceeding the amount lost may be added by the moisture-adjusting unit40. Thus, hydrogen bonds can be more reliably formed in the manufacturedsheet S because the moisture dispersed and lost in the sheetmanufacturing apparatus 100 can be satisfactorily replenished.

The processing capacity of the moisture-adjusting unit 40 can beappropriately designed and adjusted in response to the manufacturingcapacity (throughput) of the sheet manufacturing apparatus 100. Whenpassed through the heating unit 50, the moisture supplied by themoisture-adjusting unit 40 is heated and removed by evaporation. In thiscase, the plurality of fibers in the sheet S is bonded by hydrogenbonding.

1.4. Heating Unit

The sheet manufacturing apparatus 100 of this embodiment is providedwith a heating unit 50. The heating unit 50 is arranged furtherdownstream than the moisture-adjusting unit 40 described above.

The heating unit 50 heats the mixture that was mixed by the mixing unit30 and had the moisture therein adjusted by the moisture-adjusting unit40 to cause the plurality of fibers to be mutually bonded by theadditive agents and produce a state in which hydrogen bonds are formedbetween the fibers. For example, the moisture-adjusted mixture may beformed into a web shape. In addition, the heating unit 50 may have afunction that forms the mixture into a predetermined shape.

In this specification, the phrase “defibrated material and additiveagents are bonded” refers to the state in which fibers and additiveagents in the defibrated material are difficult to separate, and to thestate in which a resin additive agent is arranged between the fibers andseparating the fibers via the additive agent becomes difficult. Bondingis a concept that includes adhesion and includes the state in which twoor more bodies are in contact and are difficult to separate. When fibersare bonded by a composite, the fibers may be parallel or intersect, anda plurality of fibers may bond to a single fiber. The phrase “fibers arehydrogen bonded” refers to partial or total bonding (adhesion) of aplurality of fibers by hydrogen bonding.

When resin, which is one constituent ingredient of the additive agents,is a thermoplastic resin, and is heated to a temperature above thevicinity of the glass transition temperature (softening point) or themelting point (if a crystalline polymer), the resin softens and melts,and later when the temperature decreases, the resin hardens. The resincan soften and come into contact with and entangle the fibers, and thefibers and additive agents can mutually bond when the resin hardens.Fibers bond with other fibers during hardening. When the resin in theadditive agents is a thermosetting resin, the fibers and the resin canbond even when heated to a temperature above the softening point, orwhen heated above the curing temperature (temperature that produces thecuring response). Preferably, the melting point, the softening point,and the curing temperature of the resin are lower than the meltingpoint, the decomposition temperature, and the carbonization temperatureof the fibers. Preferably, the types of resin and fibers are selected incombinations that produce these relationships.

Additionally, the heating unit 50 evaporates a part or all of themoisture contained in the moisture-adjusted mixture. Thus, hydrogenbonds can be formed between the fibers by reducing (removing) the watermolecules between the fibers. Preferably, the heating unit 50 is set toa temperature above the boiling point of water, but if hydrogen bondscan be formed, heating may be to a temperature below the boiling pointof water.

The heating unit 50 may also apply pressure in addition to providingheat to the mixture. In this case, the heating unit 50 has a functionthat forms the mixture into a predetermined shape. The magnitude of theapplied pressure is appropriately adjusted for the type of sheet to beformed and can be from 50 kPa to 30 MPa. If the applied pressure issmall, a sheet with large porosity is obtained. If the applied pressureis large, a sheet with small porosity (high density) is obtained.

A specific configuration of the heating unit 50 includes heater rollers,thermopress molding apparatus, hot plates, hot air blowers, infraredheaters, and flash fixing apparatus. In the sheet manufacturingapparatus 100 of this embodiment shown in FIG. 1, the heating unit 50 isconfigured from heating rollers 51. In the illustrated example, theheating unit 50 heats a web W that was pressed by the pressing unit 60,which is described later. The heating unit 50 may also have the functionof applying pressure to the web W. Then by heating the web W, fibersincluded in the web W can be bonded together by additive agents and byhydrogen bonds.

In the illustrated example, the heating unit 50 is configured to heatand apply pressure to the web W sandwiched between rollers, and has apair of heating rollers 51. The respective center axes of the pair ofheating rollers 51 are parallel. The heating unit 50 may be configuredfrom parallel plate presses, in addition to being configured fromrollers. In this case, a buffer unit, which is not shown, is provided asneeded to temporarily give slack to the web that is being transferredwhile being pressed. Also, by configuring the heating unit 50 fromheating rollers 51, the sheet S can be formed while the web W iscontinuously transferred compared to when the heating unit 50 isconfigured as a parallel plate pressing unit.

FIG. 3 schematically shows the configuration in the vicinity of theheating unit 50 in the sheet manufacturing apparatus 100. The heatingunit 50 in the sheet manufacturing apparatus 100 of this embodiment isprovided with a first heating unit 50 a arranged upstream in thetransfer direction of the web W and a second heating unit 50 b arrangeddownstream. Each of the first heating unit 50 a and the second heatingunit 50 b is provided with a pair of heating rollers 51.

A guide G that assists in the transfer of the web W is arranged betweenthe first heating unit 50 a and the second heating unit 50 b.

For example, the heating rollers 51 are composed of hollow cored bars 52of aluminum, iron, or stainless steel. A separation layer 53 of a tubecontaining fluorine such as tetrafluoroethylene-perfluoroalkylvinylethercopolymer (PFA) or polytetrafluoroethylene (PTFE) or a fluorine coatingsuch as PTFE is provided on the surfaces of the heating rollers 51. Anelastic layer of silicone rubber, urethane rubber, or cotton may beprovided between the cored bar 52 and the separation layer 53. Byproviding this elastic layer, when the pair of heating rollers 51 ispressing with a heavy load, the pair of heating rollers 51 can beuniformly in contact in the axial direction of the heating rollers 51.

A heating material 54 such as a halogen heater is provided in the centerpart of the cored bar 52 as a heating means. The temperatures of theheating rollers 51 and the heating material 54 are obtained by atemperature-detecting unit, which is not shown. The drive of the heatingmaterial 54 is controlled on the basis of the obtained temperatures.Thus, the surface temperatures of the heating rollers 51 can bemaintained at predetermined temperatures. The web W being transferredcan be heated and pressurized by passing the web W between the heatingrollers 51. The heating means is not limited to a halogen heater and maybe, for example, heating means by a contact-free heater or heating meansthat uses hot air.

The illustrated heating unit 50 is an example with two groups of a pairof heating rollers 51. However, when heating rollers 51 are used as theheating unit 50, the number and arrangements of the heating rollers 51are not limited and can have any configuration within the scope of beingable to achieve the above actions. The configuration of the heatingrollers 51 in each heating unit 50 (thicknesses and materials of theseparation layer, elastic layer, and cored bar; diameters of rollers)and the load pressing on the heating rollers 51 may differ in eachheating unit 50.

As described above, resin contained in the additive agents is fused bypassing through the heating unit 50 (heating process), easily becomesentangled with the fibers in the defibrated material, and causes thefibers to bond by hydrogen bonding. The mixture of moisture-adjusteddefibrated material and additive agents is passed through the heatingunit 50 and becomes the sheet S.

In this specification, the sheet S refers to a configuration in which aplurality of fibers is bonded by resin in two and three dimensions andis bonded by hydrogen bonding.

The sheet in this specification is not limited to a sheet shape and maybe shaped like a film, a board, a web, or a shape with indentations andbumps. Also, the sheet in this specification can be classified as paperand nonwoven material. For example, paper includes raw materials of pulpor used paper formed into sheets, and includes recording paper,wallpaper, wrapping paper, colored paper, drawing paper, Kent paper,etc. with the objectives of writing and printing. Nonwoven material isthicker and has lower strength than paper, and includes typical nonwovenmaterials, fiberboard, tissue paper, paper towels, cleaning cloths,filters, liquid-absorbing materials, sound-absorbers, cushions, mats,etc.

1.5. Actions and Effects

According to the sheet manufacturing apparatus 100 of this embodiment,it is possible to manufacture the sheet S provided with bonding forcesbetween the fibers of the defibrated material by resin and hydrogenbonding. That is, the fibers of the defibrated material can be bondedtogether by resin and by hydrogen bonds. In addition, in the sheetmanufacturing apparatus 100 of this embodiment, moisture is adjustedafter the mixture of defibrated material and additive agents isobtained. Therefore, as compared with adding moisture before the mixtureis obtained, the additive agents can be better dispersed among thefibers in the sheet S. Thus, according to this sheet manufacturingapparatus 100, a sheet S having good water resistance and highmechanical strength can be manufactured by a dry type method.

For example, even if the bonding forces of the hydrogen bonds betweenthe fibers are reduced when a sheet S manufactured by the sheetmanufacturing apparatus 100 of this embodiment is placed in ahigh-humidity environment or is dampened by water, bonding in thedefibrated material by resin can be maintained. Therefore, the sheetmaintains mechanical strength and has good water resistance that resistsshape deformation.

Furthermore, according to the sheet manufacturing apparatus 100 of thisembodiment, because there is a moisture-adjusting unit 40 for adjustingthe moisture of the mixture of defibrated material and additive agents,hydrogen bonds can be adequately elicited as the bonding forces betweenthe fibers forming the sheet S even when a dried defibration object wasused or when installed in a low-humidity environment.

1.6. Other Configurations

The sheet manufacturing apparatus 100 of this embodiment can havevarious configurations that include a crushing unit, a classifier unit,a pressing unit, a screening unit, a refining unit, a deposition unit,and a cutting unit in addition to the defibrating unit, the mixing unit,the moisture-adjusting unit, and the heating unit, which were describedabove. Additionally, a plurality of configurations can be provided asneeded for the defibrating unit, the mixing unit, the heating unit, thecrushing unit, the classifier unit, the pressing unit, the screeningunit, the refining unit, the deposition unit, and the cutting unit.

1.6.1. Pressing Unit

The sheet manufacturing apparatus 100 of this embodiment may have apressing unit 60. In the sheet manufacturing apparatus 100 shown in FIG.1, the pressing unit 60 is arranged downstream of the mixing unit 30 andthe moisture-adjusting unit 40, and upstream of the heating unit 50. Thepressing unit 60 applies pressure without adding heat to a web W thatwas passed through the refining unit 70 and the deposition unit 75,which are described later, formed into a sheet shape, and had themoisture adjusted therein. Consequently, the pressing unit 60 does nothave a heating means, such as a heater. That is, the pressing unit 60 isconfigured to perform the so-called calendering process.

The gaps (distances) between fibers in the web W are reduced to increasethe density of the web W by applying pressure (compress) to the web W inthe pressing unit 60. As illustrated in FIGS. 1 and 3, the pressing unit60 is configured so that the web W is sandwiched between rollers thatapply pressure thereto, and has a pair of pressure rollers 61. Therespective center axes of the pair of pressure rollers 61 are parallel.The pressing unit 60 of the sheet manufacturing apparatus 100 of thisembodiment is provided with a first pressing unit 60 a that is arrangedupstream in the transfer direction of the web W and a second pressingunit 60 b arranged downstream. The first pressing unit 60 a and thesecond pressing unit 60 b are each provided with a pair of pressurerollers 61. In addition, a guide G to assist in the transfer of the webW is arranged between the first pressing unit 60 a and the secondpressing unit 60 b.

The pressure rollers 61 are configured from, for example, a hollow orsolid cored bar 62 of, for example, aluminum, iron, or stainless steel.An anti-rust process such as electroless nickel plating or a magnetitefilm may be applied to, or a separation layer of a tube containingfluorine such as tetrafluoroethylene-perfluoroalkylvinylether copolymer(PFA) or polytetrafluoroethylene (PTFE), or a fluorine coating such asPTFE may be formed on the surfaces of the pressure rollers 61. Inaddition, an elastic layer based on silicone rubber, urethane, or cottonmay be provided between the cored bar 62 and the surface layer describedabove. By providing the elastic layer, the pair of pressure rollers 61that press at a high load can be in uniform contact in the axialdirection of the pressure rollers 61.

Because the pressing unit 60 only applies pressure without heating,resin in the additive agents does not melt. In addition, almost none ofthe moisture in the mixture is removed because the pressing unit 60 onlyapplies pressure without heating.

The sheet manufacturing apparatus 100 of this embodiment is providedwith the pressing unit 60 (first pressing unit 60 a, second pressingunit 60 b) and the heating unit 50 (first heating unit 50 a, secondheating unit 50 b). In this example, the heating unit 50 appliespressure to the web W. Preferably, the pressing force of the pressingunit 60 is set to be larger than the pressing force of the heating unit50. For example, preferably, the pressing force of the pressing unit 60is set from 500 to 3000 kgf, and the pressing force of the heating unit50 is set from 30 to 200 kgf. By setting the pressing force of thepressing unit 60 to be greater than that of the heating unit 50, thedistances between the fibers included in the web W can be adequatelyshortened by the pressing unit 60. By heating and applying pressure inthis state, a thinner, high-density, and high-strength sheet can beformed.

In addition, in the sheet manufacturing apparatus 100 of thisembodiment, the diameter of a pressure roller 61 is set to be greaterthan the diameter of a heating roller 51 as shown in FIGS. 1 and 3. Inother words, the diameter of a pressure roller 61 arranged upstream inthe transfer direction of the web W is larger than the diameter of aheating roller 51 arranged downstream. Because the diameter of thepressure roller 61 is large, the web W still in the unpressurized statecan be gripped and efficiently transferred. In addition, the web W thatpassed through the pressure rollers 61 is in the pressurized state andis easily transferred. Therefore, the diameters of the heating rollers51 arranged further downstream may be smaller than those of the pressurerollers 61. Thus, the configuration of the apparatus can be smaller. Thediameters of the heating rollers 51 and the pressure rollers 61 areappropriately set to correspond to the thickness and properties of themanufactured web W.

The illustrated pressing unit 60 is an example of two groups of pressurerollers 61 pairs. When the pressing unit 60 is used and pressure rollers61 are used as the pressing unit 60, the number and arrangements of thepressure rollers 61 are not limited. Any configuration is possiblewithin the scope of being able to achieve the above actions.

Furthermore, the only part that can come into contact with the web Wbetween the pressure rollers 61 of the pressing unit 60 and the heatingrollers 51 of the heating unit 50 is the guide G as the web receivingpart that is able to support the web W from below. Consequently, thedistance between the pressure rollers 61 and the heating rollers 51 canbe shortened. In addition, because the web W with pressure applied israpidly heated and pressurized, spring back of the web W can besuppressed, and a high-strength sheet can be formed.

The configuration described above for the pressing unit 60 (pressurerollers 61) and the heating unit 50 (heating rollers 51) is intended fora thin, high-density, high-strength sheet. For example, it is intendedfor paper rather than nonwoven material. On the other hand, the use of aplanar pressing unit as the heating unit 50 is intended for a relativelythick sheet. This is for a sheet that is thick and takes a long time totransmit heat to the entire web because the planar pressing unit is incontact with the web W for a longer time than the use of a heatingroller. The pressing unit 60 does not have to be upstream of the planarpressing unit. This case is intended for a relatively low-density sheetbecause there is no high-density compression by the pressing unit 60.The planar pressing unit is used for nonwoven material rather thanpaper. In the case of nonwoven materials, if the fibers have lowmoisture content when formed as a sheet, after the planar pressing unitheats and applies pressure, the thickness increases. Changes in thethickness after the application of heat and pressure can be suppressedby having the planar pressing unit apply heat and pressure after themoisture was adjusted.

1.6.2. Classifier Unit

In the sheet manufacturing apparatus 100 illustrated in FIG. 1, theclassifier unit 63 is arranged upstream of the mixing unit 30 anddownstream of the defibrating unit 20. The classifier unit 63 separatesand removes resin particles and ink particles from the defibratedmaterial. This can increase the proportion of fibers in the defibratedmaterial. Preferably, the classifier unit 63 uses an airflow classifier.The airflow classifier generates a rotating airflow to separateaccording to the sizes and densities of the materials classified bycentrifugal force. The classification point can be adjusted by adjustingthe velocity of the airflow and the centrifugal force. Specifically, theclassifier unit 63 may be a cyclone, an elbow jet, or an eddyclassifier. In particular, the cyclone has a simple configuration andcan be suitably used as the classifier unit 63. In the descriptionbelow, the cyclone is used as the classifier unit 63.

The classifier unit 63 has an introduction port 64, a cylinder part 65connected to the introduction port 64, an inverted cone part 66 that isarranged below and connected to the cylinder part 65, a lower dischargeport 67 that is arranged in the lower center part of the inverted conepart 66, and an upper discharge port 68 that is arranged in the uppercenter part of the cylinder part 65.

In the classifier unit 63, airflow that carries the defibrated materialintroduced from the introduction port 64 changes to circumferentialmotion in the cylinder part 65 that has an outer diameter fromapproximately 100 mm to 300 mm. Thus, fibers in the defibrated materialand fine powder, such as resin powder and ink powder in the defibratedmaterial, can be separated by the centrifugal force applied to theintroduced defibrated material. Components with many fibers aredischarged from the lower discharge port 67 and introduced through thepipe 86 to the mixing unit 30. In addition, fine particles aredischarged to outside of the classifier unit 63 from the upper dischargeport 68 through the pipe 84. In the illustrated example, the pipe 84 isconnected to a receiving unit 69 and the fine particles are collected inthe receiving unit 69. Because fine particles such as resin powder orink powder are discharged to the outside by the classifier unit 63,excess resin can be kept out of the defibrated material even when theresin is supplied by an additive agent supply unit 88 to be describedlater.

Separation of the fibers and the powder by the classifier unit 63 wasdescribed, but complete separation is not possible. For example,relatively small fibers and low-density fibers are sometimes dischargedto the outside with the powder. In addition, relatively high-densitypowder and powder entangled with fibers are sometimes dischargeddownstream with the fibers.

In addition, when the raw material is a pulp sheet and not used paper,the sheet manufacturing apparatus 100 does not have to include aclassifier unit 63 because fine powder, such as resin particles or inkparticles, are not included. Conversely, when the raw material is usedpaper, preferably, the configuration of the sheet manufacturingapparatus 100 includes a classifier unit 63 in order to produce goodcolor tone in the manufactured sheet. In addition, because a betterwhiteness level is more often sought for paper than for nonwovenmaterial, the classifier unit 63 is often used in the manufacture ofpaper and not used in the manufacture of nonwoven material.

1.6.3. Crushing Unit

The sheet manufacturing apparatus 100 may include a crushing unit 10. Inthe sheet manufacturing apparatus 100 shown in FIG. 1, the crushing unit10 is arranged upstream of the defibrating unit 20. The crushing unit 10cuts the raw material like pulp sheets or fed-in sheets (e.g., A4-sizeused paper) in the air to produce the defibration object. The shapes andsizes of the defibration object are not particularly limited. Thedefibration object may be, for example, several square centimeters. Inthe illustrated example, the crushing unit 10 can have a crushing blade11 and use the crushing blade 11 to cut the fed-in raw material. Anautomatic feeding unit, which is not shown, to continuously feed in theraw material may be provided in the crushing unit 10.

A specific example of the crushing unit 10 is a shredder. In theillustrated example, the defibration object that was cut up by thecrushing unit 10 is transferred through a pipe 81 after being receivedby a hopper 15 to the defibrating unit 20. Pipe 81 passes through theintroduction port 21 of the defibrating unit 20.

1.6.4. Refining Unit

The sheet manufacturing apparatus 100 may have a refining unit 70. Inthe sheet manufacturing apparatus 100 shown in FIG. 1, the refining unit70 and the deposition unit 75 are arranged downstream of the mixing unit30. The refining unit 70 introduces the mixture that passed through pipe86 (mixing unit 30) from the introduction port 71 and is able to dropthe mixture while the mixture is dispersed in the air. In addition, inthis example, the sheet manufacturing apparatus 100 has a depositionunit 75 that forms the mixture that was dropped from the refining unit70 and deposited in the air by the deposition unit 75 into the shape ofa web W.

The refining unit 70 refines entangled defibrated material (fibers).Furthermore, the refining unit 70 refines the entangled resin when resinin the additive agents supplied from the additive agent supply unit 88is in a fibrous form. The refining unit 70 acts to uniformly deposit themixture in the deposition unit 75 to be described later. The term“refine” includes the action of breaking up tangles and the action ofuniform deposition. The refining unit 70 has the effect of uniformdeposition if there are no tangles.

The refining unit 70 may be a sieve. An example of the refining unit 70is a rotating sieve that can be rotated by a motor. Here, the sieve ofthe refining unit 70 may not have a function for screening specificobjects. That is, the “sieve” used as the refining unit 70 refers to anobject provided with a net (filter, screen). The refining unit 70 maydrop down all of the defibrated material and additive agents introducedto the refining unit 70.

1.6.5. Deposition Unit

The sheet manufacturing apparatus 100 may have a deposition unit 75.Defibrated material and additive agents that passed through the refiningunit 70 are deposited by the deposition unit 75. As shown in FIG. 1, thedeposition unit 75 has a mesh belt 76, stretching rollers 77, and asuction mechanism 78. The deposition unit 75 may be configured toinclude tension rollers, which are not shown.

The deposition unit 75 forms the web W of the mixture that was droppedfrom the refining unit 70 and deposited in the air (equivalent to a webforming process combined with the refining unit 70). The deposition unit75 has a mechanism that deposits the mixture dispersed uniformly in theair by the refining unit 70 onto the mesh belt 76. The configuration mayalso have a moisture-adjusting unit 40 that adjusts the moisture of themixture that dropped from the refining unit 70.

An endless mesh belt 76 that forms the mesh stretched by stretchingrollers 77 (4 stretching rollers in this embodiment) is arranged belowthe refining unit 70. The mesh belt 76 is moved in one direction by atleast one rotation of the stretching rollers 77.

The suction mechanism 78 is provided vertically below the refining unit70 as the suction unit that generates airflow vertically downwardthrough the mesh belt 76. The mixture dispersed in the air by therefining unit 70 can be suctioned to the top of the mesh belt 76 by thesuction mechanism 78. Thus, the mixture dispersed in the air can besuctioned, and the discharge velocity from the refining unit 70 can beincreased. As a result, the productivity of the sheet manufacturingapparatus 100 can be improved. In addition, a downflow can be formed inthe drop path of the mixture by the suction mechanism 78 and preventdefibrated material and additive agents from becoming entangled duringthe drop.

An elongated web W of uniformly deposited mixture can be formed bydropping the mixture from the refining unit 70 while the mesh belt 76 ismoving. The term “uniformly deposited” means that the deposited materialis deposited to a nearly uniform thickness and roughly identicaldensity. However, the portion that becomes a sheet may be uniformbecause not all of the deposited material is manufactured into a sheet.“Nonuniform deposition” means that the deposition is not uniform.

The mesh belt 76 can be made of metal, resin, cloth, or nonwovenmaterial, or any material if the mixture can be deposited thereon andairflow can pass therethrough. The hole size (diameter) of the mesh belt76 is, for example, from 60 μm to 250 μm.

If the hole size of the mesh belt 76 is less than 60 μm, the suctionmechanism 78 may have difficulty forming stable airflow. If the holesize of the mesh belt is greater than 250 μm, the fibers of the mixtureenter the mesh, for example, and uneveness in the surface of themanufactured sheet becomes substantial. In addition, the suctionmechanism 78 may be configured from a sealed box with a window havingthe desired size opened below the mesh belt 76 to suction air fromoutside the window to produce negative pressure inside the box withrespect to the outside air.

As described above, a web W containing a large amount of air and ispliant and swollen is formed by passing through the refining unit 70 andthe deposition unit 75 (web forming process). Next, as shown in FIG. 1,the web W formed on the mesh belt 76 is transferred by rotational motionof the mesh belt 76. In this example, the web W formed on the mesh belt76 is transported to the moisture-adjusting unit 40, pressing unit 60,and heating unit 50.

1.6.7. Screening Unit

Although not shown, the sheet manufacturing apparatus 100 of thisembodiment may also have a screening unit. The screening unit can screendefibrated material, which was produced by defibration in thedefibrating unit 20, according to the lengths of the fibers. The removalof fine resin powder in the classifier unit 63 described above wasexplained, but the screening unit may also have this function.Consequently, the screening unit is arranged downstream of thedefibrating unit 20 and further upstream than the refining unit 70. Inaddition, when provided, the screening unit may be arranged furtherupstream than the moisture-adjusting unit 40.

The screening unit may be a sieve. The screening unit has a net (filter,screen) to screen objects having sizes that can pass through the net andobjects having sizes that cannot pass through. The screening unit can beconfigured similar to the refining unit 70 described above, and has afunction that removes a portion of the ingredients and does not pass allof the materials introduced by the refining unit 70. An example of thescreening unit is a rotating sieve that can be rotated by a motor. Thenet in the screening unit can be a metal net, an expanded metal of astretched metal panel with openings, or a perforated metal formed byusing a pressing apparatus to form holes in a metal plate.

By providing a screening unit, fibers and particles smaller than thesize of the net openings that are contained in the defibrated materialor the additive agents can be separated from fibers, undefibratedpieces, and lumps that are larger than the net openings. Then, thescreened materials are selected and used to correspond to themanufactured sheet. In addition, the materials removed by the screeningunit may be returned to the defibrating unit 20.

The sheet manufacturing apparatus 100 of this embodiment may have aconfiguration other than the configurations described above and mayhave, when appropriate, a plurality of configurations that correspond tothe objectives and include the configuration described above. The numberand order of configurations are not limited, and can be appropriatelydesigned to correspond to the objectives.

1.6.8. Other Apparatus

In the sheet manufacturing apparatus 100 of this embodiment, a firstcutting unit 90 a and a second cutting unit 90 b are arranged downstreamof the heating unit 50 as the cutting unit 90 to cut the sheet in thedirection intersecting the transport direction of the web W (web Wpassed by the heating unit 50 that becomes a sheet S). The cutting unit90 may be provided as needed. The first cutting unit 90 a is providedwith a cutter and cuts a continuous sheet S into individual sheets atthe cutting positions set at specified lengths. In addition, the secondcutting unit 90 b for cutting the sheet S in the transfer direction ofthe sheet S is arranged downstream of the first cutting unit 90 a in thetransfer direction of the sheet S. The second cutting unit 90 b isprovided with a cutter to cut at predetermined positions in the transferdirection of the sheet.

Thus, sheets S having the desired size can be formed. The cut sheets Sare stacked in a stacker 95.

Although not shown, a cooling unit for cooling the sheet S heated by theheating unit 50 may be arranged downstream of the heating unit 50. Thecooling unit can be configured from, for example, cooling rollers. Byproviding a cooling unit, cooling of the resin can be rapid, and thestructure of the sheet S can be rapidly fixed. Thus, the apparatus canhave improved throughput and a smaller size.

2. Sheet Manufacturing Method

The sheet manufacturing method of the embodiment uses the sheetmanufacturing apparatus 100 described above and includes a defibratingprocess that defibrates the defibration object in the air, a mixingprocess that mixes in the air additive agents including resin into thedefibrated material, a moisture-adjusting process that adjusts themoisture of the mixture that mixes the defibrated material and theadditive agents, and a heating process that heats the moisture-adjustedmixture. Detailed descriptions of the defibration object, defibratedmaterial, fibers, resins, additive agents, moisture adjustment, andheating are omitted because they are similar to the above descriptionsof the sheet manufacturing apparatus.

The sheet manufacturing method of this embodiment may include in theappropriate order at least one process selected from the group ofprocesses: a process that cuts in the air the defibration object such aspulp sheet and used paper as the raw material, a classifying processthat classifies from the defibrated material impurities (toner orpaper-strengthening agent) and fibers shortened by defibration (shortfibers) in the air, a screening process that screens long fibers fromthe defibrated material (long fibers) and undefibrated fiber pieces thatwere insufficiently defibrated, a dispersion (refining) process thatdrops the mixture while dispersing the mixture into the air, a sheetforming process that deposits the dropped mixture in the air to forminto a web shape, a pressing process that applies pressure to the web,and a cutting process that cuts the formed sheet. Detailed descriptionsof these processes are omitted because they are similar to the abovedescriptions of the sheet manufacturing apparatus.

According to this sheet manufacturing method, a sheet S can bemanufactured in which the bonding forces between the fibers of thedefibrated material are provided by resin. For example, when a sheet Smanufactured by this sheet manufacturing method is placed in ahigh-humidity environment or dampened by water, even if the bondingforces of the hydrogen bonds in the defibrated material are reduced, thebonds in the defibrated material are maintained by resin. Therefore,mechanical strength is maintained, and water resistance that makes shapedeformation difficult is good. Furthermore, according to this sheetmanufacturing method, hydrogen bonds can be elicited as the bondingforces between the fibers comprising the sheet S even when drieddefibration object is used or when set up in a low-humidity environmentbecause there is a moisture-adjusting process that adjusts the moistureof the mixture of defibrated material and additive agents. By using thisdry type method, a sheet S with good water resistance and highmechanical strength can be manufactured. Furthermore, in this sheetmanufacturing method, because moisture is adjusted in the mixtureobtained in the mixing process that mixes defibrated material andadditive agents, compared to the addition of moisture before the mixtureis obtained, additive agents are well dispersed between the fibers inthe sheet S. Therefore, the strength of the manufactured sheet S can befurther improved.

3. Other Items

In this specification, the term “uniform” as in uniform dispersion ormixing indicates that the relative positions of one ingredient withrespect to other ingredients in the materials that are defined asingredients having two or more types, or two or more phases are uniformthroughout the entire system, or mutually identical or essentially equalin each part of the system. In addition, uniformity of the coloring anduniformity of the color tone indicates uniform density without darkeningof the color when the sheet is viewed from above. However, similarly,the distances between all of the resin are not the same, and sometimesthe density is not the same density throughout.

In this specification, the terms with equivalent meanings are used suchas uniform, same, and equal gap; or density, distance, and dimension.Preferably, these are equivalent, but complete equivalence is difficult,and offsets in which accumulated values of unequal errors andfluctuations are included.

Conventionally, when defibrated material and additive agents are mixed,a mixture with good uniformity or a good sheet was relatively easy toobtain because coagulation of the additive agents is suppressed by theactions of the water when water is present in the system (wet typesystem). Today, however, there is not necessarily an establishedtechnology for the manufacture of recycled paper that manufacturesrecycled paper from used paper in a dry type system. According tostudies by the inventors, one reason is the difficulty in creating aprocess in a dry type system that mixes fibers and paper strengtheningagents (e.g., resin particles). That is, when fibers and resin powderare simply mixed without any device in a dry type system, and the fibersand the resin powder are not adequately mixed together and then used inthe formation (deposition) of a sheet to obtain paper, the dispersion ofresin is nonuniform in the paper surface, and the paper will haveinadequate mechanical strength. In addition, when fibers and resinparticles are mixed in a dry type system, the resin particles readilycoagulate by coagulation forces, such as van der Waals forces, and areeasily dispersed nonuniformly.

In the actions and effects described above, the fibers are not onlybonded by additive agents, but are bonded by hydrogen bonds. Hydrogenbonds develop because moisture is added, but the bonding of fibers byadditive agents is further strengthened by providing some degree ofmoisture to the fibers. In either case, a strong sheet can be producedin a dry type system independent of the state of the raw materials andthe environment of the apparatus by adjusting the moisture of themixture of fibers and additive agents.

The present invention is not limited to the embodiments described aboveand may have various forms. For example, the present invention includesconfigurations essentially identical to the configurations described inthe embodiments (configurations with identical functions, methods, andeffects, or configurations with the same objectives and effects). Thepresent invention includes configurations in which parts not essentialto the configurations described in the embodiments are replaced. Inaddition, the present invention includes configurations that have thesame actions and effects as the configurations described in theembodiments or configurations that can achieve the same objectives. Thepresent invention includes configurations that add known technologies tothe configurations described in the embodiments. For example, the web Wis a single layer in the embodiment described above, but may havemultiple layers, or may have layers of nonwoven materials and papercreated separately.

GENERAL INTERPRETATION OF TERMS

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts. Finally, terms of degree such as“substantially”, “about” and “approximately” as used herein mean areasonable amount of deviation of the modified term such that the endresult is not significantly changed. For example, these terms can beconstrued as including a deviation of at least ±5% of the modified termif this deviation would not negate the meaning of the word it modifies.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing descriptions of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A sheet manufacturing apparatus comprising: adefibrating unit configured to defibrate a defibration object in theatmosphere; a mixing unit configured to mix, in the atmosphere, additiveagents including resin into a defibrated material that has beendefibrated by the defibrating unit; a moisture-adjusting unit configuredto adjust moisture in a mixture of the defibrated material and theadditive agents, which has come out from the mixing unit; and a heatingunit configured to heat the mixture that has been moisture-adjusted bythe moisture-adjusting unit.
 2. The sheet manufacturing apparatusaccording to claim 1, further comprising a deposition unit configured todeposit the mixture that has been mixed by the mixing unit, themoisture-adjusting unit being configured to adjust the moisture of themixture deposited by the deposition unit.
 3. The sheet manufacturingapparatus according to claim 1, wherein the moisture-adjusting unit isconfigured to add moisture to the mixture such that a moisture contentis 5 parts by weight to 12 parts by weight with respect to 100 parts byweight of the mixture before moisture adjustment.
 4. The sheetmanufacturing apparatus according to claim 1, wherein themoisture-adjusting unit is configured to add moisture to the mixturesuch that a moisture content after moisture adjustment of the mixture isgreater than a moisture content included in the defibration object. 5.The sheet manufacturing apparatus according to claim 1, wherein themoisture-adjusting unit is configured to vary content of moisture to beadded to the mixture in accordance with at least one of conditions ofmoisture content of the defibration object, humidity of the environment,and temperature.
 6. The sheet manufacturing apparatus according to claim1, further comprising a deposition unit including a belt and configuredto deposit, on the belt, the mixture that has come out from the mixingunit, the moisture-adjusting unit being configured to add moisture tothe mixture deposited on the belt.
 7. The sheet manufacturing apparatusaccording to claim 1, further comprising a pressing unit configured topress the mixture that has been moisture-adjusted before the mixturethat has been moisture-adjusted is heated.